[PATCH v8 1/3] dt-bindings: drm/bridge: Document Cadence MHDP bridge bindings

[Laurent Pinchart]

Hi Swapnil,

Thank you for the patch.

On Thu, Aug 06, 2020 at 01:34:30PM +0200, Swapnil Jakhade wrote:
> From: Yuti Amonkar <yamonkar at cadence.com>
> 
> Document the bindings used for the Cadence MHDP DPI/DP bridge in
> yaml format.
> 
> Signed-off-by: Yuti Amonkar <yamonkar at cadence.com>
> Signed-off-by: Swapnil Jakhade <sjakhade at cadence.com>
> Reviewed-by: Rob Herring <robh at kernel.org>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  .../bindings/display/bridge/cdns,mhdp.yaml    | 139 ++++++++++++++++++
>  1 file changed, 139 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/bridge/cdns,mhdp.yaml
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp.yaml b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp.yaml
> new file mode 100644
> index 000000000000..dabccefe0983
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp.yaml
> @@ -0,0 +1,139 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/display/bridge/cdns,mhdp.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: Cadence MHDP bridge
> +
> +maintainers:
> +  - Swapnil Jakhade <sjakhade at cadence.com>
> +  - Yuti Amonkar <yamonkar at cadence.com>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - cdns,mhdp8546
> +      - ti,j721e-mhdp8546
> +
> +  reg:
> +    minItems: 1
> +    maxItems: 2
> +    items:
> +      - description:
> +          Register block of mhdptx apb registers up to PHY mapped area (AUX_CONFIG_P).
> +          The AUX and PMA registers are not part of this range, they are instead
> +          included in the associated PHY.
> +      - description:
> +          Register block for DSS_EDP0_INTG_CFG_VP registers in case of TI J7 SoCs.
> +
> +  reg-names:
> +    minItems: 1
> +    maxItems: 2
> +    items:
> +      - const: mhdptx
> +      - const: j721e-intg
> +
> +  clocks:
> +    maxItems: 1
> +    description:
> +      DP bridge clock, used by the IP to know how to translate a number of
> +      clock cycles into a time (which is used to comply with DP standard timings
> +      and delays).
> +
> +  phys:
> +    maxItems: 1
> +    description:
> +      phandle to the DisplayPort PHY.
> +
> +  ports:
> +    type: object
> +    description:
> +      Ports as described in Documentation/devicetree/bindings/graph.txt.
> +
> +    properties:
> +      '#address-cells':
> +        const: 1
> +
> +      '#size-cells':
> +        const: 0
> +
> +      port at 0:
> +        type: object
> +        description:
> +          Input port representing the DP bridge input.
> +
> +      port at 1:
> +        type: object
> +        description:
> +          Output port representing the DP bridge output.

I've got a chance to study the J721E datasheet, and it shows the DP
bridge has 4 inputs, to support MST. Shouldn't this already be reflected
in the DT bindings ? I think it should be as simple as having 4 input
ports (port at 0 to port at 3) and one output port (port at 4).

The bindings are ABI, so care must be taken to support all features and
avoid future changes that would break backward compatibility. It's fine
if the driver doesn't implement this feature yet.

> +
> +    required:
> +      - port at 0
> +      - port at 1
> +      - '#address-cells'
> +      - '#size-cells'
> +
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: ti,j721e-mhdp8546
> +    then:
> +      properties:
> +        reg:
> +          minItems: 2
> +        reg-names:
> +          minItems: 2
> +    else:
> +      properties:
> +        reg:
> +          maxItems: 1
> +        reg-names:
> +          maxItems: 1
> +
> +required:
> +  - compatible
> +  - clocks
> +  - reg
> +  - reg-names
> +  - phys
> +  - ports
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    bus {
> +        #address-cells = <2>;
> +        #size-cells = <2>;
> +
> +        mhdp: dp-bridge at f0fb000000 {
> +            compatible = "cdns,mhdp8546";
> +            reg = <0xf0 0xfb000000 0x0 0x1000000>;
> +            reg-names = "mhdptx";
> +            clocks = <&mhdp_clock>;
> +            phys = <&dp_phy>;
> +
> +            ports {
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +
> +                port at 0 {
> +                    reg = <0>;
> +                    dp_bridge_input: endpoint {
> +                        remote-endpoint = <&xxx_dpi_output>;
> +                    };
> +                };
> +
> +                port at 1 {
> +                    reg = <1>;
> +                    dp_bridge_output: endpoint {
> +                        remote-endpoint = <&xxx_dp_connector_input>;
> +                    };
> +                };
> +            };
> +        };
> +    };
> +...

-- 
Regards,

Laurent Pinchart